1. Field of the Invention
The present invention relates to a remote control system, in particular for adjustable articles of furniture and office, hospital and nursing home equipment, such as beds, chairs, tables, patient lifters, etc. The invention also relates to an adjustable article of furniture and to a power driven actuator.
2. The Prior Art
The description of the invention will be based on hospital beds, as these illustrate the problems underlying the invention quite well.
A hospital bed has an electrical appliance with a linear actuator for adjusting the backrest part of a hinged support section as well as an actuator for adjusting its legrest part. In addition, the support section as a whole may be raised and lowered, as well as be caused to assume a tilted position (Trendelenburg""s or anti-Trendelenburg""s position). Adjustment of the support section as a whole is performed by two actuators. Beds of this type are described e.g. in U.S. Pats. No. 5,161,274 and 5,205,004, both to J. Nesbit Evans and Co. Ltd.
The actuators are connected to a control box, which also contains a power supply. The actuators and the control box are positioned below the bottom of the bed. The control box is operated by a hand control connected to it by wire. The hand control must be capable of being operated by the patient himself and also by the hospital staff, such as patient care staff, nurses, orderlies, doctors, and cleaning staff.
The wire for the hand control constitutes a problem per se, and this is not lessened by the fact that it must be relatively long even though a helically twisted wire is used. Lying in bed, the patient must be able to reach and operate the hand control, while the staff must be able to operate it, standing at the foot end of the bed. Further, the wire must not be in the way when the patient goes to bed or is taken to bed by the staff, nor of course when the patient gets out of bed. This may take place from both the one and the other side of the bed. Of course, a hand control might be arranged at each end of the bed, but this is much too expensive. After each use, the bed must be washed, and here the helically twisted wire constitutes a problem since it is difficult to clean. Another drawback of the wire is that, because of its length and the movement of it from one end to the other, it will frequently get squeezed between the movable parts of the bed and thereby be damaged or even be cut completely.
To avoid the wire for the hand control, a wireless hand control might be considered, but this presents other problems. One of the problems is actually the storage of the hand control. It must be readily accessible for both patient and staff. In an emergency it is no good that the patient has packed the hand control away in a side table, if, e.g., the bed is to be placed in Trendelenburg""s position immediately. At a hospital with several hundreds of beds it is altogether no good having a corresponding number of loose hand controls. Connecting these to the beds by a wire is no solution to the problems.
A hand control based on an infrared transmitter moreover involves a problem of mounting the receiver at a place accessible to all parties. Lying in bed, the patient will naturally direct the hand control toward the foot end, while the staff will direct it toward the head end, which is psychologically unfortunate for the patient.
The other common wireless option is a hand control based on radio communication. A problem of using such a solution where several beds are frequently placed in the same room, like at a hospital, is that the activation of a hand control must only cause a reaction from precisely the desired bed. Therefore, it is necessary to use hand controls which are dedicated to communicating precisely with a given bed, and this emphasizes the problem of keeping track of the individual hand controls. Now there must not only be one for each bed, but a quite specific hand control. One way of performing the dedication of the hand control is to mount a code recognition circuit in the individual receiver. This, however, involves the use of rather complicated electronics, and therefore adds to the costs, and radio communication per se is more expensive than infrared communication. Further, it gives rise to considerations that the allocated frequency ranges are crowded, involving risks of interference, and that radio communication per se presents a latent risk of operational disturbances of the often highly sensitive electronic equipment which is used at hospitals.
Considering the problems, it is thus not evident to change from a wired hand control to a wireless one, particularly not when the solution previously used is the absolutely cheapest one seen in relation to a wireless control.
The object of the invention is to provide a wireless remote control system in which a dedicated remote control for operating each individual unit is avoided, while ensuring that only one selected unit can be operated at a time.
Accordingly, the invention provides a remote control system which is characterized by
utilizing at least one hand control and one or more control units,
the hand control and the control units comprising transmit and receive antennas,
the control units including a transmitter for transmitting a signal with a frequency which is unique to the individual control unit,
the remote control including a receiver for reception of this signal from the control unit from which the signal is strongest relative to the hand control, as well as a transmitter for transmitting a signal with a frequency which is a whole multiple of the received signal and, via a phase locking circuit, is in phase with the received signal, and means for coding the transmitted signal with instructions,
the control units including a receiver for receiving the signal from the hand control, as well as means for determining whether the received signal is in phase with the signal formed by the circuit of the control unit, and means for decoding and executing the instructions on the received signal.
With this embodiment of a remote control system, an arbitrary hand control in the system can adapt itself to the control unit from which the signal is strongest, and subsequently communicate with the control unit. Thus, there is no need for hand controls which are dedicated to the individual control unit, as an arbitrary control unit may be used in connection with all the control units. If it is desired to communicate with a specific control unit, then it is just necessary to assume a position where it is known with certainty that the signal from there is the strongest.
Taking hospital conditions as an example again, it is now possible to equip the patients with an arbitrary hand control for the control of the bed which they might be given, just as the staff may be equipped with a single remote control which can operate all the beds. In terms of organizing, there are substantially no limits to the administration of the hand controls, and, e.g., a remote control might conceivably be placed in a holder on each bed or the associated side table and one in a holder on the wall or the door to the ward for use by the staff.
The inventive concept provides several options of realizing the invention adapted to specific fields of use, and the invention may also be used where infrared communication has traditionally been used previously. The remote control may thus be us ed in connection with TV, video players, hi-fi systems, etc., it being ensured of course that the signal of the remote control does not interfere with the radio/television signal.
The remote control system may be constructed such that the control units constantly transmit signals, but where this is not desired for some reason, the system may be arranged so that the transmitters of the control units are normally turned off and are turned on only upon activation of a remote control, understood in the way that it is only the closest one or ones within a given radius from the remote control that are turned on.
In case of, e.g., beds, this also applies to sickbeds, beds in dwellings and at hotels, the range of the transmitter need not be very great in reality, since the user is normally in bed or quite close to it, and it may even be an advantage to construct the remote control system such that the range is quite short. The same problems actually apply to practically all types of adjustable articles of furniture, including office furniture. In these cases, the structure may be made simple, just as the consumption of energy will be low. The extent and shape of the field may moreover be determined by the antenna means used, and a loop of wire is thus particularly useful in connection with furniture. The field is here within the boundary of the loop and perpendicular to it, while radiation outside the boundary of the loop has a modest range.
In some situations one-way communication is sufficient, viz. the remote control can communicate with the control unit, but in other situations it is desirable with a duplex where the control unit can send information back to the remote control. In such an embodiment, the control unit is provided with means for coding the transmitted signal with instructions, while the hand control has means for decoding and executing the instructions on the received signal.
Rather than manufacturing the control units intentionally with a unique signal, which is complicated in terms of production, advantage is taken of the fact that electronic components may be manufactured with given values of tolerance. It is realized in this connection that with quite ordinary standard components a unique signal is obtained because of the spreading on their value. The components have a value +/xe2x88x92 a tolerance and this is this spreading in the value, which is exploited to obtain the unique signals. Using components with the same value will result in a signal with a unique frequency due to the deviations in the values within the tolerance given. Although, hereby, only the order of magnitude of the frequency of the signal is known and not the exact value, this is in fact quite immaterial since automatic phase locking to the signal takes place. The use of standard components has evident advantages in terms of production, just as standard components per se give a lower cost price. This means that a remote control system according to the invention will be able to compete with a solution with a cabled control.
In an embodiment of the invention, coding of the transmitted signals with instructions may take place by phase-shifting selected phases 180 degrees, so that a shifted phase, e.g., represents a digital 0 and a non-shifted phase represents a digital 1, and a decoder, upon reception of the signal, can detect whether the individual phases are phase-shifted relatively to what is expected.
In order to be able to determine quite uniquely whether the signal has been phase-shifted or not, the control unit is arranged such that its transmitter sweeps in narrow ranges.
The invention also relates to an adjustable article of furniture, preferably a bed, a chair and a table equipped with at least an electric motor for performing adjustments of the article of furniture, the article being equipped with a remote control system as stated above. It should be stressed that the term article of furniture is used in its widest sense and also covers hospital, nursing home, hospice, clinic, institution, office and hotel furniture.
In a particular embodiment of the article of furniture, the antenna means, preferably in the form of a wire loop, are integrated in it. This may be in a chassis frame or in a tabletop.
The invention moreover relates to a power driven actuator and a power driven lifting column equipped with a remote control system as stated above. Power driven actuator or lifting column should also be taken to mean a system consisting of several power driven actuators or lifting columns having a common control.
Besides the invention relates to an article of furniture, preferably a bed, a chair or a table having at least one adjustable element, such as a backrest of a bed or chair or a tabletop of a table, a drive unit, such as an actuator or lifting column with an electric motor to execute the adjustments of said adjustable element, a control box with an electrical or electronic control for operating said drive unit, a hand control comprising a cabinet with keys for communication with said control box, wherein said furniture is having an antenna means, said control box furnished with or being connected to a radio receiver and said receiver being connected to the antenna means, and said hand control being furnished with a radio transmitter and antenna means for communicating with said radio receiver for operating said adjustable element of said article of furniture.